Qt and Git

I'm new to both Qt and Git, so this question could easily go on a newbie git form.

What files should I be tracking in my project? The obvious answer is anything I want backed up; however, do I need all these extra files or just my code?

For example, when I create a project Qt makes three directories: ProjectDir, ProjectDir-build, and ProjectDir-debug.
Do I need to track all three of these directories? Or can I just track the main dir that has the .pro file, all my .cpp and .h files?

This is my first Qt project, and first time using git. Any advice would be nice.